1. Field of the Invention
The present invention relates to a sheet member discharge mechanism that can be applied to image-forming machines such as copiers, printers and facsimiles.
2. Description of the Prior Art
In an image-forming machine such as a copier, a printer or a facsimile as is widely known, an image is formed on the sheet members which may be common papers, successively, and the sheet members are discharged onto a receiving member and are stacked thereon. At the end of the sheet member conveyer passage, there is disposed a sheet member discharge mechanism which includes an upper discharge roller and a lower discharge roller. The sheet member is conveyed in a predetermined direction being nipped between the upper discharge roller and the lower discharge roller, and is discharged onto a receiving means disposed under the sheet member discharge mechanism.
The sheet members discharged and stacked on the receiving means are, as required, corrected for their stacked state and, in many cases, are, further, conveyed through a predetermined conveyer passage. In particular, when the sheet members discharged and stacked on the receiving means are further conveyed through a predetermined passage, the receiving member constituting the receiving means is set to be as short as possible (to be slightly longer than, for example, a maximum length of the sheet member that is discharged) in the direction in which the sheet members are discharged from the standpoint of realizing the image-forming machine in a compact size. Besides, the upstream end of the receiving member is positioned under the lower discharge roller as viewed in the direction of discharge of the sheet members without separating the receiving member toward the downstream in the direction of discharge from the upper discharge roller or the lower discharge roller. According to this constitution, the trailing edge of the sheet member that has passed the nipping portion between the upper discharge roller and the lower discharge roller, must further move downward along the peripheral surface of the lower discharge roller to arrive at the upstream end of the receiving member located under the lower discharge roller. According to the conventional mechanism for conveying the sheet members, however, slipping occurs between the trailing edge of the sheet member and the peripheral surface of the lower discharge roller; i.e., the trailing end of sheet member fails to move along the peripheral surface of the lower discharge roller and tends to stay covering the upper peripheral surface of the lower discharge roller. Should that happen, the next sheet member is interrupted from being discharged and, besides, it becomes difficult to correct the stacked state of the discharged sheet members.
It is therefore an object of the present invention to provide a novel and improved sheet member discharge mechanism which is capable of reliably lowering the trailing edge of a sheet member down to an upstream end of a receiving member positioned under a lower discharge roller by moving the trailing edge of the sheet member along the peripheral surface of the lower discharge roller after the trailing edge of the sheet member has passed a nipping portion between an upper discharge roller and the lower discharge roller.
In order to accomplish the above-mentioned object, the present invention provides a sheet member discharge mechanism comprising an upper discharge roller and a lower discharge roller for conveying a sheet member in a predetermined direction while nipping it therebetween; wherein
at least one push-down member is disposed downstream of the nipping portion between said upper discharge roller and said lower discharge roller as viewed in a direction of conveying the sheet member, said push-down member being allowed to move between an ascended position and a descended position and is urged to said descended position; and
said push-down member is moved to said ascended position by said sheet member acting upon said push-down member while the sheet member is being conveyed by said upper discharge roller and said lower discharge roller that work in cooperation, and said push-down member moves to said descended position to push down the trailing edge of the sheet member after the trailing edge of the sheet member has passed the nipping portion between said upper discharge roller and said lower discharge roller.
It is desired that said push-down member is extending toward the downstream being inclined downward from above the nipping portion between said upper discharge roller and said lower discharge roller down to below the nipping portion thereof at both said ascended position and said descended position.
Preferably, the lower surface of said push-down member includes an upstream portion and a downstream portion which extends toward the downstream being inclined downward at a predetermined bending angle xcex1which is from 10 to 30 degrees with respect to said upstream portion; when said push-down member is at said ascended position, said upstream portion on the lower surface of said push-down member extends toward the downstream being inclined downward at an inclination angle xcex21 of from 10 to 30 degrees, and said downstream portion extends toward the downstream being inclined downward at an inclination angle xcex31 of from 20 to 60 degrees; and when said push-down member is at said descended position, said upstream portion on the lower surface of said push-down member extends toward the downstream being inclined downward at an inclination angle xcex22 of from 30 to 50 degrees, and said downstream portion extends toward the downstream being inclined downward at an inclination angle xcex32 of from 40 to 80 degrees.
It is desired that when said push-down member is brought to said descended position, the tip of said push-down member is located at a position which is lower than a center axis of said lower discharge roller but is higher than the lowermost end of said lower discharge roller and when said push-down member is brought to said ascended position, the tip of said push-down member is located at a position lower than said nipping portion between said upper discharge roller and said lower discharge roller but is higher than the center axis of said lower discharge roller.
It is desired that said push-down member is urged to said descended position by its own weight.
The push-down member may have a rectangular shape and can be formed of a synthetic resin plate.
Plural ribs can be formed on at least the upstream portion on the lower surface of said push-down member, the plural ribs extending in the direction of conveying the sheet member maintaining a distance in the direction of width.
It is desired that the push-down member is mounted to swing about a center axis thereof which is substantially in agreement with the center axis of said upper discharge roller.
Desirably, when said push-down member is brought to said descended position, the lower surface of said push-down member comes in contact with the lower discharge roller, whereby said push-down member is prevented from swinging in excess of said descended position.
The push-down member can be arranged in a plural number maintaining a distance in the direction of width.